1. Field of the Invention
The present invention relates to a sheet film pack containing therein a plurality of sheet films stacked one atop another, and a film pack holder for holding the sheet film pack such that the sheet films can be exposed in turn with a camera to which the pack holder is attached.
In particular, the present invention relates to a sheet film pack and a film pack holder wherein the sheet film pack is changeable without the need for removal of the film pack holder from the camera.
2. The Known Prior Art
Large format cameras, such as view cameras and studio cameras, are utilized for taking photographs that are to be printed in a large size or at a large print magnification. Such a photograph is used, for example, in a catalog. These large format cameras use a sheet film or a photographic plate 4.times.5 inches or more in size. Such a large format photographic medium is especially desirable in those cases which require sharpness of the image.
In some conventional large format cameras, the photographic plate or the sheet film is removed after each exposure from the camera, so as to load a new plate or film. This film loading system is inconvenient for taking photographs in rapid succession.
An improvement, a film holder is disclosed in U.S. Pat. No. 3,021,772 and Japanese Laid-Open Utility Model Appln. No. 50-22029, which is constituted of an external frame attachable to a camera and an internal frame mounted in the external frame. Such a film holder is also sold by Fuji Photo Film Co., Ltd. under the trademark "4.times.5 Quick Changer". The internal frame accommodates several sheet films stacked one atop another, and has an exposure opening for exposing the topmost of the stacked sheet films. A sliding lid is provided for closing the exposure opening in light-tight fashion. The internal frame is also slidable into and out of the external frame.
By alternately sliding the lid and the internal frame relative to the external frame, which is stationary because it is attached to the camera, the topmost sheet film is moved, after each exposure, into the bottom of the internal frame, and in turn, the next sheet film is placed on the top, that is, in the exposure position. Therefore, it is possible to expose successively several sheet films merely by sliding the lid and the internal frame, without the need for changing the film holder.
However, because the internal frame of the above-described film holder cannot be separated from the external frame, it is necessary to prepare a plurality of such film holders in order to take a larger number of photographs in succession than the number of sheet films available in each film holder. Accordingly, the known film holder is inconvenient for outdoor photography, especially in the mountains, because it is necessary to carry about the camera and the film holders. Also in studio photography, the known film holder is inconvenient to handle because it is necessary to detach the external frame of the film holder from the camera after all the available sheet films therein are exposed, and to attach another film holder to the camera in order to load unexposed sheet films.
To solve these problems, a system was developed and published in Japan on Aug. 21, 1992 as Japanese Laid-Open Patent Appln. No. 4-234025. This system is constituted by a film pack and a pack holder which correspond to the internal and external frames of the known film holder, respectively, but the film pack is removable from the pack holder. This system makes it possible to change and use a plurality of film packs in turn in combination with a single pack holder, and is therefore improved as to portability and ease of film loading.
The above-described system also requires the sliding of the film pack and a lid thereof in order to expose each sheet film. If the lid or the film pack is wrongly manipulated, the sheet film will be accidentally improperly exposed before or after the desired exposure. To avoid such a malfunction, the above-described known film holder is provided with a latch mechanism for preventing accidental sliding. As the internal frame cannot be removed from the external frame, the latch mechanism can be easily incorporated in the film holder. But the known latch mechanism must be manually actuated. Therefore, it is possible to forget to actuate the latch mechanism, thereby causing photographic fogging or double exposure.
The film pack of this known system has openings formed in one end of the film pack housing, for ejecting the exposed sheet films from the film pack housing and for receiving the same into the film pack housing. These openings are provided with respective light-trapping members.
However, if intense light, such as sunlight from a bright sky, falls directly onto the openings, the light may enter the interior of the film pack through the openings and produce photographic fog on the sheet films.
The film pack of this known system further has a film counting mechanism for counting and displaying the number of the exposed sheet films contained therein. Therefore, even if the film pack is changed before all the available sheet films have been exposed, the number of the exposed films in the respective film packs is displayed. However, the film counting mechanism increases the cost of manufacturing the film pack. For this reason, the film pack is relatively expensive, and the housing is used repeatedly. The user must remove the exposed sheet films from the film pack in a dark room or in a light-tight bag, and insert the exposed sheet films into a light-tight envelop or box, after which the exposed sheet films are forwarded to a photofinisher for development and printing.
Furthermore, when loading unexposed sheet films, the user must also insert the unexposed sheet films individually into thin film frames, hereinafter referred to as film sheaths, and thereafter set the sheet films inserted in the respective film sheaths, hereinafter referred to as sheet film units, in the film pack housing. This film loading operation must also be performed in a dark room. Accordingly, the film loading and unloading operations necessary with the known system are very cumbersome.